Script

jQuery(function($){
    $('button').click(function(){
        $(':disabled','#formDemo').attr('disabled','');
        return false;
    });
});

HTML

<form>
<table summary="入力可否の切り替え" id="formDemo">
    <tr>
        <th class="check">入力切り替え</th>
        <td class="check">
            <button>入力可に</button>
        </td>
    </tr>
    <tr>
        <th><label for="postZip01">郵便番号</label></th>
        <td>
            〒<input type="text" name="postZip" id="postZip01" value="" disabled="disabled" />
        </td>
    </tr>
    <tr>
        <th><label for="zip01">都道府県</label></th>
        <td>
            <select name="zip01" id="zip01" disabled="disabled">
                <option value="" selected>選択してください</option>
                <option value="1">北海道</option>
                <option value="2">青森県</option>
                <option value="3">岩手県</option>
                <option value="4">宮城県</option>
                <option value="5">秋田県</option>
                <option value="6">山形県</option>
                <option value="7">福島県</option>
                <option value="8">茨城県</option>
            </select>
        </td>
    </tr>
    <tr>
        <th><label for="zio02">市区町村</label></th>
        <td><input name="zip02" id="zip02" type="text" value="" disabled="disabled" /></td>
    </tr>
    <tr>
        <th><label for="zip03">番地</label></th>
        <td><input name="zip03" id="zip03" value="" type="text" disabled="disabled" /></td>
    </tr>
    <tr>
        <th><label for="zip04">アパート・マンション名</label></th>
        <td><input name="zip04" id="zip04" value="" type="text" disabled="disabled" /></td>
    </tr>
</table>
</form>

Demo